Method and means for controlling the output of electrical machines



June 24, 1930. c; STOKES TRICAL MACHINES METHOD AND MEANS FOR CONTROLLING THE OUTPUT OF ELEC 1924 2 Sheets-Sheet 1 Filed NOV. 10

I INVENTOR.

WW \wssa June 24,1930, L; STOKES 1,768,165

METHOD AND MEANS FOR CONTROLLING THE OUTPUT OF ELECTRICAL MACHINES Filed 1924 2 Sheets-Sheet 2 IN V EN TOR.

Y gwozm Patented June 24, 1930 Y CHARLES LAWRENCESTCKES, 013 LOS ANGELES," CALIFORNIA METKQD AND MEANS FOR CONTROLLING THE OUTPUT OF ELECTRICAL MACHINES Application filed-November 10, 1924. Serial no. 748,933.

My invention relates to improvements for controllin automatically the output of electrical mac ines such as electrical generators and the like.

The principal object of my invention is to automatically control the electrical output of a generator driven by an internal combustion engine.

A further object of my invention is to automatically control the output of a generator by the vacuum of an internal combustion engine which drives the generator.

A further object of my invention is to automatically and manually regulate the input from an electric generator to a storage battery.

A further object is to rovide an electric generator so wound as to incorporate my invention.

Referring to the drawings in which the same numbers indicate like arts v Fig. 1 is a diagram embo ying features of my invention.

Fig. 2 is a view showing the ap lication of '25 my invention to an internal com ustion engine.

Fig. 3 is a vertical section of part of Fig. 2. Fig. 4 is a front view of Fig. 3. Fig. 5 is a sectional detail of part of Figs.

! 1 and 2.

Fig. 6 is an alternative construction of Fig. 5.

Fig. 7 shows an alternative adaptation of my invention.

Fig. 8 shows a part section and diagrammatic view of Fig. 7. Fig. 9 shows an alternative construction of Fig. 8.

Fi 1O Fig.

Fig. 11 shows a sectional detail of Figs. 7 and 10.

In the operation of automobiles and other vehicles impelled by an internal combustion engine, it is customary to provide an electric generator driven by the engine for charging a storage battery. Such generators are of different construction, a great many of which atthe present time embod what is known as a third brush system whic regulates the outshows a diagram of the circuit in put of the generator to the end that at maximum engine speedsthere will not be more than a maximum given input to the storage battery therefrom.

Such generator systems as are now used generally provide a maximum charging cur-- generator 1 is provided with a shunt field.

winding 2 and also with an opposed shunt field winding 3. The shunt winding 3 is so arranged with respect to the shunt winding 2 that the efi'ect of current flow through 3 tends to neutralize the current flow through 2 for influencing the output of l and 3 is what is often known as a bucking winding. Interposed in series in the shunt winding 3 is a variable resistance 4 connected by a acuum pipe 5 to the carburetor 6 of an internal combustion engine 7.

The main circuit leading from 1 is grounded at 8 and connects to the battery 9 whence it is grounded at 10.

A light circuit 11 is grounded at 12 and includes a switch 13 and a lamp, or series of lamps, 15.

Referring to Fig. 5 it will be seen that the vacuum pipe 5 is connected to 4 which includes a chamber 16 made of non-conducting material and containing a number of carbon discs 17 mounted on a rod 18 which rod is threaded into a piston 19 having a stem 20 extending outside of 16 and surrounded by a spring 21 adapted to press against a nut 22.

The description of Fig. 5 as given is that of a well known construction of carbon pile which may be made in a variety of forms to obtain the same result i. e., the increase, or

decrease, of resistance through the pile with decrease or increase of ressure on the pile. The carbon pile 16 is p aced in series in the shunt winding 3 and the wires 23 and 2 1 are respectively joined to opposite ends of the carbon pile by a metallic brush 25 and a lock nut 26 which latter is threaded on to 20 for firmly holding 24.

The generator 1 is mounted on engine 7 in any customary fashion to be driven thereby at predetermined speed and the pipe 5 is connected to the carburetor 6 on the atmosphere side of throttle 27 and pipe 5 is preferably connected with the smallest constriction in 6 which is generally a choke throat, or venturi, 28.

A pipe 29 is connected to the pipe 5 which leads to the dash 30 of an automobile, being bifurcated at its upper end into'a pipe 30 and a pipe 31. 30 passes through the dash or instrument board 30 and is controlled by a needle valve 32. 31 passes through the dash and is controlled by the lighting switch 13. Referring to Figs. 3 and 4, it will be seen that when the switch 13 is moved to the left all the lights of the automobile will be on and therefore the pipe 31 will be wide open whereas when 13 is moved to the right, the lights are dimmed, or only partly in use, and in this position the pipe 31 is only partly open, the reasons for which will be later explained.

In the operation of the usual four cycle internal combustion engine, the vacuum induced in carburetor 6, below the throttle 27, will vary proportionately with the speed of the engine, that is to say the vacuum will be very low at low engine speeds and will increase to a maximum at the highest engine speeds and these differences of vacuum are now made use of by me for varying the pressure in the carbon pile 16 for decreasing or increasing the resistance in the shunt winding 3 whereby the output of generator 1 will be maintained at a desired figure.

If it be desired to maintain the charging rate from 1 to the battery 9 at six amperes at any given speed, and if it be assumed that this speed is when the throttle 27 is closed, the vacuum applied from 28 through 5 to the interior of 16 will be a minimum and therefore the atmospheric pressure tending to compress the carbon discs 17 will be a minimum with the result that the resistance offered by the carbon discs 17 will be a maximum and therefore the current passing through 3 will be a minimum permitting the shunt 2 to exercise its influence on the generator 1 whereby six amperes will be supplied to the battery 9.

The vacuum applied through 5 may be adjusted by the needle valve 32 because the opening or closing of 32 will permit moreor less air to be induced through the holes 33 for breaking the vacuum applied to 16 so that any desired amperage may be delivered to 9, this regulation by means of 32 being accomplished when the pipe 31 is fully closed by the switch 13. Upon the opening of throttle 27, the speed of engine 7 and .generator 1 will increase thereby increasing the output of 1 but at the same time the vacuum at 28 will also increase causing increased atmospheric pressure on the carbon pile 16 whereby an increased current will flow through 3 and maintain the desired output of 1 through the neutralizing effect of 3 on 2.

Further increase of speed correspondingly increases the pressure in 16 and correspondingly lowers the resistance therein so that the bucking coil 3 at all speeds tends to hold the output of 1 at a predetermined minimum. If now it be desired to switch on the current to the lamps 15, in full, the switch 13 will be turned to the left thus uncovering the pipe 31 permitting sufficient air to flow therethrough so that any vacuum being applied to 5 will be reduced to the end that the resistance offered by the carbon pile 16 will be increased thus permitting an increased output from 1 to compensate for the current being used in the lamps 15. If the lamps consume six amperes, the amount of air passing through 31 responsive to the engine vacuum will be just suflicient air to permit the battery to still charge at the given rate of six amperes. If it only be desired to burn some of the lamps, or to use say three amperes current, the throwing of switch 13 to the right will only partly uncover the pipe 31 thereby decreasing the flow of atmosphere therethrough and only partially increasing the resistance in 16. This partial opening of 31 is accomplished by the annular are 34 forming part of 13.

It is of course understood that a circuit breaker (not shown) is inserted in the main circuit to prevent the battery 9 from passing its charge in full back through the generator 1. In this manner it may be seen that automatic regulation is provided under all conditions resulting in increased output of the engine 7 at critical times because there will be a variation in the vacuum at 28 under given road conditions. For instance,' at thirty-five miles an hour on the level, there will be a certain vacuum at 28, while at thirty-five miles an hour on a grade, .the vacuum at 28 will rise with increased opening of 27. In consequence, on going up a grade the increased vacuum will decrease the resistance in 16 thus reducing the load on the generator which would otherwise be added to the output of engine 7 at a more or less critical time.

It is of course obvious that a similar resistance, as illustrated in Fig. 6, may be interposed in a single ordinary shunt winding of a generator whereby an increase of engine While my invention has been described as utilizing the direct effect of engine vacuum for actuating a variable resistance, it may be used in' conjunction with other forms of automatically operated variable resistances, with or without the aid of engine vacuum and also in conjunction with a third brush system.

In Figs. 7 and 9, the exhaust pipe of engine 7 is shown as enclosing a variable resistance 36 which is composed of a nonconducting material, such as porcelain, forming a sealed tube containing a metallic oxide, such as magnesium oxide or cerium oxide, or other equivalents, to resistance of which the current flow is known as negative resistance, or the resistance decreases with increase of heat applied thereto.

The heat of exhaust gases from an internal combustion engine varies with the speed of the engine and ranges from about 400 F. at idling speed to about 1400 F. at sixty miles per hour. Therefore with increasing engine speed the resistance offered by 36 will decrease permitting the shunt winding 3 to automatically increase its neutralizing efiect on shunt winding 2, thus maintaining or governing the output of -1.- In this case the variable resistance 4 may be dispensed with or used as desired for a given efl'ect, or range. While the form of the variable resistance shown in Fig. 5, or that shown in Fig. 6 may be employed in connection with the form of the device shown in Figs. 7 and 9, preferably the variable resistance shown in Fig. 6 is employed, under conditions where the speed of the motor is substantially constant and the load varies, as in trucking in level coun'- tries.

Since the generator is operated by the engine, the speed of the generator will vary with the speed of the vehicle, but in order to maintain the vehicle at a constant speed, owing to the dilferent road conditions, it is necessary to vary the position of the throttle. The wider the throttle, the more gas consumed, and consequently the hotter the resistance element 36 will become. This alone would increase the strength of the current.

the decreased resistance through the resistance element 36, thereby maintaining substantially a constant output of the genera-. tor 1. I

In Fi 8, a metallic resistance 38 composed oiron, a chromium alloy or other equivalent, may be directly exposedto the,

exhaust gases in 35 for obtainin the same result, the lead wires 23and 24 ing connected thereto through insulating plugs 39. The lead 23 is broken by a bell crank switch 40, one arm of which 41 is made of nonconducting material and the switch 40 is con trolled by the action of a bi-metallic thermostat 42 attached to 35.

The switch gap in 23' is normally closed by a high resistance 43 and in the present instance 4 with its controls may or may not be used as desired fora particularrange.

With the construction shown in Fig. 8, the

shunt 3 may be dispensed with, the resistance 38 being placed in series with the shunt winding 2 because theresistance of the metal mentioned is positive resistance, i. e., the resist ance increases with the increasing heat applied thereto. Therefore, increasing engine speed will increase the resistance in theshunt winding 2 and maintains, or governs, the

able resistance 4 in connection with the device shown in Figs. 7 and 9-.

When coasting and operating engine 7 without ignition, or when the engine 7 is cold, the thermostat 42 acts to break the shunt circuit 2 to the end that the decreased resistance of 38 will be partly compensated 1 by the high resistance 43 thereby controlling the output of 1. When hot exhaust gases again flow through 35. the thermostat 42 acts to close the shunt circuit by closing switch 40 and keeping the same closed as long as engine 7 is delivering power.

A third brush automatic control is shown in Figs. 10 and 11 wherein the current flowing through the shunt winding 2 is controlled by the position of a third brush 44 on the commutator of 1. Brush 44 is generally mounted on an insulated revolving frame 45 which can be adjustably moved, but the frame 45 being within housing of the enerator 1 the same is very difficult of access and hard to adjust. By attaching a control device to the frame 45, I am enabled to automatically control the setting of 44 in accordance with engine speed.

This control device comprises a chamber 46 containing a piston 47 to which is fixed a rod 48 made of non-conducting material for moving 45. 46 is open to atmosphere at 49 and the movements of 47, 48, 45 and 44 is governed by the engine vacuum a plied throu h 5, a spring 50 eing supplie for norma y 5 maintaining the same in a predetermined position when engine 7 is stopped.

YVith the increasing engine speed, the brush 44 will move in the direction of the arrow shown in Fig. 10 and therefore the output 10 of 1 will decrease, or be maintained at a desired figure. With decreasing engine speed a reverse action will take place.

I claim In combinatioman engine, a storage battery, a generator operated by said engine for charging said battery, and means controlled by the heat of the exhaust and by the suction of said engine for maintaining a substantially constant output from said generator.

Signed at WVilmington, in the county of Los Angeles, and State of California, this 28th day of October, A. D. 1924.

CHARLES LAWRENCE STOKES. 

